On Thu, June 3, 2010 10:15, Garrett D'Amore wrote: > Using a stripe of mirrors (RAID0) you can get the benefits of multiple > spindle performance, easy expansion support (just add new mirrors to the > end of the raid0 stripe), and 100% data redundancy. If you can afford > to pay double for your storage (the cost of mirroring), this is IMO the > best solution.
Referencing "RAID0" here in the context of ZFS is confusing, though. Are you suggesting using underlying RAID hardware to create virtual volumes to then present to ZFS, or what? > Note that this solution is not quite as resilient against hardware > failure as raidz2 or raidz3. While the RAID1+0 solution can tolerate > multiple drive failures, if both both drives in a mirror fail, you lose > data. In a RAIDZ solution, two or more drive failures lose your data. In a mirrored solution, losing the WRONG two drives will still lose your data, but you have some chance of surviving losing a random two drives. So I would describe the mirror solution as more resilient. So going to RAIDZ2 or even RAIDZ3 would be better, I agree. In an 8-bay chassis, there are other concerns, too. Do I keep space open for a hot spare? There's no real point in a hot spare if you have only one vdev; that is, 8-drive RAIDZ3 is clearly better than 7-drive RAIDZ2 plus a hot spare. And putting everything into one vdev means that for any upgrade I have to replace all 8 drives at once, a financial problem for a home server. > If you're clever, you'll also try to make sure each side of the mirror > is on a different controller, and if you have enough controllers > available, you'll also try to balance the controllers across stripes. I did manage to split the mirrors accross controllers (I have 6 SATA on the motherboard and I added an 8-port SAS card with SAS-SATA cabling). > One way to help with that is to leave a drive or two available as a hot > spare. > > Btw, the above recommendation mirrors what Jeff Bonwick himself (the > creator of ZFS) has advised on his blog. I believe that article directly influenced my choice, in fact. -- David Dyer-Bennet, d...@dd-b.net; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
